The present of accumulations of radioactive radon gas in homes and similar structures has in recent years become the focus of a great deal of attention. The gradual release of radon gas into the atmosphere from the soil is nothing new, but the problem has become acute because of increased efforts to make structural dwellings more thermally secure and thus more likely to accumulate harmful gases.
Radon is produced by the gradual decay of solid radioactive elements in the soil. While geographic regions that contain large concentrations of solid radioactive elements in the soil will likewise release larger amounts of radon into the atmosphere, it is not the mere release, even in such areas, that is of concern. The uninterrupted movement of radon into the atmosphere is generally at such a slow rate that little or no health hazard is posed by the release alone.
The concern that has arisen in recent years began with the discovery of large concentrations of radon gas that had accumulated in dwellings and similar structures. It soon became apparent that it was not the rate at which radon gas was given off by the soil, but the failure of dwellings to allow radon and other contaminants to continue on into the atmosphere. In an effort to make homes more energy efficient, builders have attempted to physically and thermally seal the structures as tight as possible. While this did indeed succeed in reducing thermal losses into the atmosphere, it also succeeded in retaining and accumulating contaminated air.
One factor in the degree of contaminant accumulation is the structure of the building itself and more specifically the structure of the support system in contact with the ground. In recent years, more and more homes are being built upon what is called a slab foundation. The effect of this type of foundation is to act as a cap to contain gases from the soil, allowing them to escape only when they find their way up into the house by way of cracks and intentionally placed holes in the foundation. Because modern air circulation systems will typically only recycle internal air rather than exchange it with external air, these contaminants tend to remain and accumulate within the house.
One solution to the problem that a number of existing or proposed systems utilized is the controlled exchange of inside contaminated air with fresh outside air. While this method does reduce the level of radon and other contaminants within the structure, it also tends to sacrifice the thermal integrity of the house. In addition, because these contaminant removal systems rely on the home's air circulation system, they are effective only when such system is in operation.
Those few proposed systems that avoid the exchange of interior air generally contain forced vacuum components that dramatically increase both the installation and operational costs. It would therefore be desirable and advantageous to devise a ventilation/evacuation system that would prevent the accumulation of radon gas within homes or similar structures without effecting the thermal efficiency of the home, and without incurring large installation, maintenance, and operational costs.